(57) An olefin polymerization catalyst composition comprising:
(1) a zirconium compound containing pi-bonded organic ligands and having the formula:
CpmZrAnXq
wherein:
Cp represents an unsubstituted or substituted cyclopentadienyl group,
m represents 1 or 2 or 3;
A represents a halogen or hydrogen atom or a C₁ -C₆ alkyl group, a metalloalkyl group
or a group of the formula:
 wherein:
R represents a C₁ to C₁₀ alkyl group, a hydrogen, or halogen atom or a metalloalkyl
group;
X represents a halogen or hydrogen atom or C₁ to C₆ alkyl group; n represents 0, 1
or 2; and q represents 0, 1 or 2;
providing that q+m+n is equal to the valence of zirconium; and
(2) a catalyst activator which comprises a mixture of
(i) an organoaluminum compound having the formula:
Rp 'Al X' (k-p) or R3 'Al₂ X3'
wherein:
R' represents a C₁ to C₆ alkyl group;
p represents 1 or 2;
X' represents a halogen atom; and
k represents the valence of aluminum; and
(ii) a dialkylmagnesium compound having the formula:
Mg Rt '' or Mg Rr ''R''' (t-r)
wherein:
R'' represents a C₂ to C₈ alkyl group;
R''' differs from R'' and represents a C₂ to C₈ alkyl group;
t represents the valence of magnesium; and
r represents 0.01 to 1.
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